Chemical process



United States Patent CHEMICAL PROCESS Edwin George Edward Hawkins, Lower Kingswood, and Irene Marianne Watt, West Ewell, England, assignors to The Distillers Company Limited, Edinburgh, Scotland, a British company No Drawing. Application July 15, 1957 Serial No. 671,735

Claims priority, application Great Brita'inJuly 26, 1956 8 Claims. (Cl. 260-448) The present invention relates to a process for the production of an aluminium alkyl sesquichloride from metallic aluminium and the corresponding alkyl chloride.

An aluminium alkyl sesquichloride is any mixture of an aluminium dialkyl chloride and an aluminium alkyl dichloride, the alkyl groups being the same in both compounds. For example aluminium ethyl sesquichloride is a mixture of the two compounds having the formula Al(C H .Cl and Al(C I-l ).Cl As usually prepared aluminium alkyl sesquichlorides consist of equimolar proportions of the two components.

Various processes are known for the manufacture of aluminium alkyl sesquichlorides, in particular, for the manufacture of aluminium ethyl sesquichloride. However, they all have one or more of the following features: (a) the reaction has to he carried out at super-atmospheric pressure, (b) the reaction is subject to long or variable induction periods and, when it does commence, it is often difficult to control, (c) there are necessarily present in the reaction mixture compounds containing labile halogen atoms other than chlorine and consequently care has to be taken to ensure that the products are not contaminated with compounds containing the other halogen atoms, (d) specially prepared, oxide free metallic aluminium is required in order that the reaction can proceed in the desired manner, and (e) they require the use of unstable or undesirable reaction initiators.

An object of the present invention is to provide an improved process for the production of aluminium alkyl sesquichlorides in which the above features can all be eliminated. In particular it is an object of the present invention to provide a process for the production of aluminium alkyl sesquichlorides which can readily be operated at atmospheric pressure using simple, readily available raw materials.

According to the present invention the process for the production of an aluminium alkyl sesquichloride from the reaction 'of aluminium with an alkyl chloride comprises reacting the aluminium with the alkyl chloride in the presence of a reaction initiator comprising a mixture of anhydrous aluminium chloride and an aluminium alkyl halide.

The aluminium used in the reaction can be in any convenient form. In order to increase the reaction rate it is best to provide as large a surface area of aluminium in the reaction mixture as possible and consequently aluminium turnings or powder are particularly useful. However, there is no need to prepare or store the aluminium in a non-oxidising atmosphere. If desired the aluminium can be present as an alloy with another metal or metals which do not interfere with the reaction, e.g. magnesium.

The alkyl chloride is chosen so that the desired aluminium alkyl sesquichloride is obtained. The most useful aluminium sesquichlorides are those derived from lower alkyl groups, i.e. alkyl groups containing not more than four carbon atoms (methyl, ethyl, propyl, butyl, etc), and the process of the present invention is partic- 2,903,469 Patented Sept. 8, 1959 ularly suited for their manufacture. The preferred aluminium alkyl sesquichloride is aluminium ethyl sesquichloride which is readily manufactured by the process of the present invention from aluminium and ethyl chloride.

One component of the reaction initiator mixture is an aluminium alkyl halide. This may be an aluminium dialkyl halide or an aluminium alkyl dihalide. Any such compound can be employed, but it is preferred that the alkyl group or groups shall correspond to those in the aluminium alkyl sesquichloride it is desired tomanufacture. Moreover, it is a particular feature of the present invention that an aluminium alkyl chloride can be employed and thus the product cannot become contaminated with compounds containing halide atoms other than chlorine. A particularly useful component of the reaction initiator mixture is the aluminium alkyl sesquichloride which it is desired to produce.

No special precautions are required with regard to the purity of any of the other components of the reaction mixture, and ordinary, commercially available grades of alkyl chlorides, aluminium chloride and aluminium alkyl halides can be employed.

The proportion of reaction initiator present in the reaction mixture can be varied considerably because very small amounts initiate the reaction and large amounts have no deleterious effects upon it. Most suitably the total amount of aluminium chloride and aluminium alkyl halide should be in excess of 2% by Weight of the reaction mixture if good initial reaction rates are to be obtained. The proportion of aluminium chloride to aluminium alkyl halide .inthe mixture forming the reaction initiator can similarly be varied considerably but, most suitably, one part by weight of aluminium chloride is used in conjunction with at least 0.5 part by Weight of the aluminium alkyl halide. Preferably approximately equal proportions by weight of the two components are used to form the reaction initiator.

The process according to the present invention can be carried out at atmospheric pressure and is thus a considerable improvement on some of the prior art processes. .If desired super-atmospheric pressures can be employed but this is unnecessary and good yields can beattained usingsimple, non-pressure apparatus.

The reaction of alumini um with an alkyl chloride under the conditions of the present invention can be brought about at normal ambient temperatures, e.g. 20 C., but preferably the reaction mixture is maintained at at least 50 C. The reaction is exothermic and consequently it is not necessary to heat the reaction mixture once the reaction has commenced.

The process of the present invention can be carried out using either an excess of aluminium or an excess of the alkyl chloride. Usually an excess of aluminium is employed because it is easier to recover from the reaction mixture for re-use than an excess of the alkyl chloride.

Most suitably the reaction is carried out by mixing the aluminium with the initiator mixture in an atmosphere of an inert gas such as nitrogen, for instance, at a temperature between 50 and C. and then adding the alkyl halide whereupon the reaction immediately begins. Conveniently the reaction mixture is held under reflux conditions so that any alkyl halide which vapourises before reacting is condensed and returned to the reaction vessel. The lower alkyl chlorides have low boiling points, for example ethyl chloride boils at about 12 C. under atmospheric pressure, and consequently any reflux condensers and the like should be operated with a suitably cooled cooling liquid.

It is a characteristic feature of the process of the present invention that the reaction is initiated by the presence ab initio of the mixture of aluminium chloride and an Example 1 Aluminium flitters (27 parts) and powdered aluminium chloride parts) are placed in a reaction vessel under nitrogen. Molten aluminium ethyl di-iodide (5 parts) is added, and the mixture heated to about 70 C. Cooled ethyl chloride (96 parts) is added dropwise and maintained under reflux by a condenser carrying cooling liquid at 30 C. Reflux ceases almost entirely after 4 hour. The mixture is heated a little longer, cooled and distilled under reduced pressure caused by a water pump. A good yield of aluminium ethyl sesquichloride is produced.

Example 2 The process described in Example 1 is followed using 5 parts of aluminium ethyl sesquichloride in place of the aluminium ethyl di-iodide to form the reaction initiator with the aluminium chloride. Again a good yield of aluminium ethyl sesquichloride is obtained.

Example 3 By proceeding along the lines set forth in Example 1 but replacing the aluminium ethyl di-iodide by a corresponding quantity of aluminium ethyl di-chloride, a similar good yield of aluminium ethyl sesquichloride is obtained.

Example 4 By proceeding along the lines set forth in Example 1, but replacing the aluminium ethyl di-iodide by the corresponding quantity of aluminium methyl di-chloride and also replacing the ethyl chloride by the corresponding quantity of methyl chloride, the aluminium methyl sesquichloride is obtained.

In like manner, the corresponding propyl and butyl derivatives may be obtained by using the corresponding aluminium propyl and butyl di-iodide (or di-chloride) respectively and, if desired, the corresponding propyl or butyl chloride, in lieu of the aluminium ethyl di-iodide and ethyl chloride used in Example 1.

We claim:

1. In a process for the production of an aluminium alkyl sesquichloride by the reaction of aluminium with an alkyl chloride, said alkyl chloride containing a maximum of four carbon atoms, the improvement of reacting the aluminium with the alkyl chloride in the presence from the beginning and throughout the reaction of an added reaction initiator consisting of a mixture of alumin ium chloride and an aluminium alkyl halide.

2. A process as claimed in claim 1, wherein the alkyl chloride is ethyl chloride.

3. A process as claimed in claim 1 wherein the alkyl group in the aluminium alkyl halide initiator is the same as the alkyl group of the alkyl halide.

4. The process as claimed in claim 1 aluminium alkyl halide initiator is a chloride.

5. A process as claimed in claim 1 wherein the reaction initiator consists of a mixture of aluminium chloride with the aluminium sesquichloride to be produced.

6. A process as claimed in claim 1, wherein the reaction initiator consists of approximately equal proportions by weight of aluminium chloride and the aluminium alkyl halide.

7. A process as claimed in claim 1, wherein the amount of reaction initiator present is in excess of 2% by weight of the reaction mixture.

8. A process as claimed in claim 1, wherein the aluminium is first mixed with the reaction initiator in the atmosphere of an inert gas at a temperature between and 100 C. and the alkyl halide is then added.

wherein the Ziegler et al. Oct. 12, 1954 Ziegler et a1. May 1, 1956 OTHER REFERENCES Article by Hnizda and Kraus in J. Amer. Chem. Soc.,

vol. (1938), p. 2276. 

1. IN A PROCESS FOR THE PRODUCTION OF AN ALUMINIUM ALKYL SESQUICHLORIDE BY THE REACTION OF ALUMINIUM WITH AN ALKYL CHLORIDE, SAID ALKYL CHLORIDE CONTAINING A MAXIMUM OF FOUR CARBON ATOMS, THE IMPROVEMENT OF REACTING THE ALUMINIUM WITH THE ALKYL CHLORIDE IN THE PRESENCE FROM THE BEGINNING AND THROUGHOUT THE REACTION OF AN ADDED REACTION INITIATOR CONSISTING OF A MIXTURE OF ALUMINIUM CHLORIDE AND AN ALUMINIUM ALKYL HALIDE. 